Use javac -release and kotlinc -Xjdk-release (#1080)

The change ensures the generated bytecode adheres to the APIs
for the target Java release.

Previously, only sourceCompatibility and targetCompatibility were used,
and they might cause issues like NoSuchMethodError when a newer javac
compiles with -target older_release.

Note: it is good to use a new an up to date javac to avoid issues
in the compiler itself, so having a proper `-release ..` configuration
is vital.

See https://www.morling.dev/blog/bytebuffer-and-the-dreaded-nosuchmethoderr

buildSrc/src/main/kotlin/pklKotlinLibrary.gradle.kts

@@ -42,5 +42,8 @@ tasks.compileKotlin {
 }
 
 tasks.withType<KotlinJvmCompile>().configureEach {
-  compilerOptions { jvmTarget = JvmTarget.fromTarget(buildInfo.jvmTarget.toString()) }
+  compilerOptions {
+    jvmTarget = JvmTarget.fromTarget(buildInfo.jvmTarget.toString())
+    freeCompilerArgs.addAll("-Xjdk-release=${buildInfo.jvmTarget}")
+  }
 }